Thesaurus of Geographic Names - A great web resource for locating political (i.e. cities) and geographic (i.e. rivers) features worldwide. Most cities contain information including latitude and longitude

U.S. Gazetteer Site
hosted by the U.S. Census Bureau where you can find information on cities within the U.S. searching on city name or postal code. Information includes the latitude and longitude.

Research models and information on Main Field Magnetism from the Colorado
Institute for Research in the Environmental Sciences (CIRES) Geomagnetism
Group

Oersted Satellite Mission. The Oersted Satellite, developed by the Danish Meteorological Institute and was launched in 1999, and is making accurate measurements of the magnetic field surrounding the Earth.